Cavity Quantum Electrodynamics with Hyperbolic van der Waals Materials

TL;DR

This paper proposes using hyperbolic van der Waals materials in cavity QED setups to achieve ultrastrong coupling in the terahertz range, enabling control of quantum emitters and exploration of new light-matter interaction regimes.

Contribution

It introduces a novel platform utilizing hyperbolic van der Waals heterostructures for ultrastrong cavity QED, especially in the terahertz spectrum, with a concrete example involving bilayer graphene and hexagonal boron nitride.

Findings

Ultrastrong coupling regime achievable with nanometer-thick hBN layers and bilayer graphene.

Hyperbolic dispersions in van der Waals heterostructures enable versatile cavity QED platforms.

Potential to explore ultrastrong light-matter interactions in 2D material systems.

Abstract

The ground-state properties and excitation energies of a quantum emitter can be modified in the ultrastrong coupling regime of cavity quantum electrodynamics (QED) where the light-matter interaction strength becomes comparable to the cavity resonance frequency. Recent studies have started to explore the possibility of controlling an electronic material by embedding it in a cavity that confines electromagnetic fields in deep subwavelength scales. Currently, there is a strong interest in realizing ultrastrong-coupling cavity QED in the terahertz (THz) part of the spectrum, since most of the elementary excitations of quantum materials are in this frequency range. We propose and discuss a promising platform to achieve this goal based on a two-dimensional electronic material encapsulated by a planar cavity consisting of ultrathin polar van der Waals crystals. As a concrete setup, we show that nanometer-thick hexagonal boron nitride layers should allow one to reach the ultrastrong coupling regime for single-electron cyclotron resonance in a bilayer graphene. The proposed cavity platform can be realized by a wide variety of thin dielectric materials with hyperbolic dispersions. Consequently, van der Waals heterostructures hold the promise of becoming a versatile playground for exploring the ultrastrong-coupling physics of cavity QED materials.